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Unformatted text preview: confidence interval from each sample statistic, over the long run 95% of our confidence intervals will contain the true population parameter (if we are using a 95% confidence level). 1 If you increase your sample size (n), you decrease your margin of error If you increase your confidence level (C), then you increase your margin of error A smaller margin of error is good because we get a smaller range of where to expect the true population parameter. Confidence interval formulas look like estimate margin of error. We write the intervals as (lower bound, upper bound). 2 Confidence Interval for a Population Mean, : x z* x
n where z* is the value on the standard normal curve with are C between –z* and z*. z* 1.645 1.960 2.576 C 90% 95% 99% (Table D in the back of the book contains more values, but these are the most common) Sample Size, n, for Desired Margin of Error, m: z * x n m 2 Note that it is the sample size, n, that influences the margin of error. The population size has nothing to do with it. Ways to reduce your ma...
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This note was uploaded on 10/09/2012 for the course STAT 301 taught by Professor Staff during the Spring '08 term at Purdue University-West Lafayette.
- Spring '08